I was referring to DEFINED as mentioned in some editions of perlfaq4. I spent a lot of time looking. I guess I looked at the wrong version of the docs today. Very frustrating to search with all the false hits on "defined". Blind tries to use it as a magic variable, a la $AUTOLOAD, and as a routine like EXISTS were all fruitless.
Given that I have no idea what it is/does, and mentioned the connection to tie; I couldn't improve my query much. The first three responses in this thread all got the context of my question so I don't think I was that vague.
I could have made it clearer that I was referring to a defined part of Perl but most got that anyway, probably from my contrast to "defined".
From Zaxo's comment I guess it is gone from Perl.
Thanks for the criticism. For me it's a battle between a tendency to run on, and on, and on, you know, a natural tendency toward verbosity and poor, complex sentence structures and being too brief.